Method of processing a contact pad, method of manufacturing a contact pad, and integrated circuit element

ABSTRACT

In a method of processing a contact pad, a passivation layer stack including at least one passivation layer is formed on at least an upper surface of a contact pad region. A first portion of the passivation layer stack is removed from above the contact pad region, wherein a second portion of the passivation layer remains on the contact pad region and covers the contact pad region. An adhesion layer is formed on the passivation layer stack. The adhesion layer is patterned, wherein the adhesion layer is removed from above the contact pad region. Furthermore, the second portion of the passivation layer stack is removed.

BACKGROUND

Embodiments of the present invention relate generally to the processingof integrated circuit elements and in particular to the processing ofcontact pads of integrated circuit elements.

Contact pads (also referred to as bond pads or short pads) are commonlyused to make external electrical contact with an integrated circuit (IC)element or device, e.g., with a chip.

SUMMARY OF THE INVENTION

A method of processing a contact pad in accordance with an embodiment ofthe invention includes forming a passivation layer stack on at least anupper surface of a contact pad region, the passivation layer stackincluding at least one passivation layer; removing a first portion ofthe passivation layer stack from above the contact pad region, wherein asecond portion of the passivation layer stack remains on the contact padregion and covers the contact pad region; forming an adhesion layer onthe passivation layer stack; patterning the adhesion layer, wherein theadhesion layer is removed from above the contact pad region; andremoving the second portion of the passivation layer stack.

A method of manufacturing a contact pad of an integrated circuit elementin accordance with another embodiment of the invention includes forminga passivation layer stack including at least one passivation layer, onan upper surface of a surface region of the integrated circuit element,the surface region including a contact pad region; removing a firstportion of the passivation layer stack from above the contact padregion, wherein a second portion of the passivation layer stack remainson the contact pad region and covers the contact pad region; forming anadhesion layer on the passivation layer stack; patterning the adhesionlayer, wherein the adhesion layer is removed from at least above thecontact pad region; removing the second portion of the passivation layerstack from above the contact pad region; and forming a reinforcementlayer stack on the contact pad region after removing the second portionof the passivation layer stack, the reinforcement layer stack includingat least one reinforcement layer.

An integrated circuit element in accordance with another embodiment ofthe invention includes a substrate, a surface region of the substrateincluding a contact pad region; and a passivation layer stack includingat least one passivation layer, formed on the surface region andadjacent to the contact pad region. In a portion of the passivationlayer stack proximate the contact pad region, an upper portion of thepassivation layer stack is removed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention. In the following description, variousembodiments of the invention are described with reference to thefollowing drawings, in which:

FIG. 1A to FIG. 1E show various processing stages of a method ofmanufacturing a contact pad of an integrated circuit element inaccordance with a first embodiment of the invention;

FIG. 2A to FIG. 2E show various processing stages of a method ofmanufacturing a contact pad of an integrated circuit element inaccordance with a second embodiment of the invention;

FIG. 3A to FIG. 3E show various processing stages of a method ofmanufacturing a contact pad of an integrated circuit element inaccordance with a third embodiment of the invention;

FIG. 4 shows a diagram illustrating a method of processing a contact padin accordance with an embodiment of the invention; and

FIG. 5 shows a diagram illustrating a method of manufacturing a contactpad in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1A shows a processing stage 100 of a method of manufacturing acontact pad of an integrated circuit element 150 in accordance with afirst embodiment of the invention. The formation of a passivation layerstack 101 is shown on an upper surface of a surface region 102 of theintegrated circuit element 150.

The surface region 102 of the integrated circuit element 150 includes acontact pad region 103 (“Met2”), and the passivation layer stack 101includes a first passivation layer 101 a formed on the upper surface ofthe surface region 102, a second passivation layer 101 b formed on thefirst passivation layer 101 a, and a third passivation layer 101 cformed on the second passivation layer 101 b.

The passivation layer stack 101 further includes a first portion 101 dand a second portion 101 e. In accordance with the first embodiment, thesecond portion 101 e of the passivation layer stack 101 corresponds to aportion of the first passivation layer 101 a that is formed on an uppersurface 103 a of the contact pad region 103, and the first portion 101 dcorresponds to a portion of the second passivation layer 101 b and thethird passivation layer 101 c that is formed on the second portion 101 eof the passivation layer stack 101.

The integrated circuit element 150 further includes a substrate thatincludes an electrically insulating layer 104. The electricallyinsulating layer 104 may be made of or may include an insulating ordielectric material such as, for example, silicon oxide (SiO₂). Ametallization region 105 (“Met1”) is formed within the electricallyinsulating layer 104 of the substrate, and is electrically connected tothe contact pad region 103 by means of a contact hole 106 (“Via”) filledwith electrically conductive material (e.g., a metal).

The surface region 102 of the integrated circuit element 150 is formedon the electrically insulating layer 104 of the substrate and includes afirst insulating layer 102 b made of silicon nitride, and furtherincludes a second insulating layer 102 c formed on the first insulatinglayer 102 b and made of silicon oxide. In accordance with otherembodiments, the first insulating layer 102 b and/or the secondinsulating layer 102 c of the surface region 102 may include or may bemade of other electrically insulating materials than the ones describedabove.

In accordance with the embodiment shown in FIG. 1A, the contact padregion 103 is embedded within the second insulating layer 102 c of thesurface region 102 with the upper surface 103 a of the contact padregion 103 being flush with the upper surface 102 a of the secondinsulating layer 102 c of the surface region 102.

The metallization region 105 may correspond to a metallization level ofthe integrated circuit element 150, and the contact pad region 103 maycorrespond to another metallization level of the integrated circuitelement 150. In accordance with one embodiment, the metallization region105 may correspond to the first metallization level (“Metal 1”) of theintegrated circuit element 150, and the contact pad region 103 maycorrespond to the second metallization level (“Metal 2”) of theintegrated circuit element 150, although in accordance with otherembodiments, the metallization region 105 and/or the contact pad region103 may correspond to other metallization levels of an integratedcircuit element, for example to two arbitrary successive metallizationlevels of an integrated circuit element. In some embodiments, themetallization region 105 may, for example, be configured as anelectrically conductive line (e.g., a metal interconnect) that may serveto form an electrical connection of one or more integrated circuits.

In accordance with some embodiments, the substrate may includeadditional layers formed below the electrically insulating layer 104,for example, other insulating or dielectric layers (e.g., intermetaldielectric layers), other electrically conductive layers such as, forexample, electrically conductive lines (e.g., metal interconnects), orother semiconducting layers (not shown in FIG. 1A). For example, inaccordance with some embodiments, one or more integrated circuits may beformed in the substrate below the insulating layer 104, and thesubstrate may include a plurality of metallization levels. In someembodiments, electrically insulating layers (e.g., intermetaldielectrics) may be formed between two successive metallization levels,and different metallization levels may be electrically connected in thevertical direction by means of one or more contact holes (vias).

In one embodiment, the contact pad region 103 is made of copper (Cu).Alternatively, the contact pad region 103 may be made of or may includeother materials such as, for example, aluminum (Al) or tungsten (W).

At least one of the passivation layers of the passivation layer stack101 may be formed by means of a deposition process such as, for example,a chemical vapor deposition (CVD) process, e.g., a plasma enhancedchemical vapor deposition (PECVD) process.

In one embodiment, the first passivation layer 101 a is formed bydepositing a first silicon nitride (SiN_(x)) layer on the upper surfaceof the surface region 102 (that is, on the upper surface 102 a of thesecond insulating layer 102 c and on the upper surface 103 a of thecontact pad region 103). The first silicon nitride layer may be formed,for example, by means of a vapor deposition process such as, forexample, a CVD process, e.g., PECVD, although other suitable depositionprocesses may be used in accordance with alternative embodiments.

In accordance with some embodiments, the first passivation layer 101 ahas a thickness in the range from about 20 nm to about 200 nm, forexample, in the range from about 50 nm to about 150 nm, e.g., 100 nm inone embodiment.

In one embodiment, the second passivation layer 101 b is formed bydepositing a silicon oxide (SiO₂) layer on the first passivation layer101 a (for example, the first silicon nitride layer). The silicon oxidelayer may be formed, for example, by means of a vapor deposition processsuch as, for example, a CVD process, e.g., PECVD, although othersuitable deposition processes may be used in accordance with alternativeembodiments.

In accordance with an alternative embodiment, the second passivationlayer 101 b may be formed by deposition of a carbide layer, for example,a silicon carbide (SiC) layer.

In accordance with some embodiments, the second passivation layer 101 b(for example, the silicon oxide layer) has a thickness in the range fromabout 100 nm to about 2 μm, for example, in the range from about 500 nmto about 1 μm, e.g., 600 nm in one embodiment.

In one embodiment, the third passivation layer 101 c is formed bydeposition of a second silicon nitride (SiN_(x)) layer on the secondpassivation layer 101 b (for example, the silicon oxide layer). Thethird passivation layer 101 c may be formed, for example, by means of avapor deposition process such as, for example, a CVD process, e.g.,PECVD, although other suitable deposition processes may be used inaccordance with alternative embodiments.

In accordance with some embodiments, the third passivation layer 101 c(for example, the second silicon nitride layer) has a thickness in therange from about 100 nm to about 2 μm, for example in the range fromabout 500 nm to about 1 μm, e.g., 550 nm in one embodiment.

The first passivation layer 101 a (e.g., the first silicon nitridelayer) of the passivation layer stack 101 may serve as a diffusionbarrier in order to prevent or reduce diffusion of material (e.g., Cumaterial) originating from the contact pad region 103.

In one embodiment, the contact pad region 103 is formed as a planarstructured pad 103 (that is, as a pad having a planar surfacetopography), for example, as a planar copper pad, for example, by meansof a single or dual damascene technology.

The integrated circuit element 150 may include other components orelements not shown in FIG. 1A, and the metallization region 105 may, forexample, be configured as a conductive line in order to electricallyconnect other elements of the integrated circuit element 150.

In accordance with some embodiments, the integrated circuit element 150is configured as a memory element or device, or as a logic element ordevice, although the integrated circuit element 150 may be configured asa different element in accordance with other embodiments.

FIG. 1B shows another processing stage 120 of the method ofmanufacturing a contact pad in accordance with the first embodiment ofthe invention. It is shown that the first portion 101 d of thepassivation layer stack 101 is removed from above the contact pad region103, wherein the second portion 101 e of the passivation layer stack 101remains on the contact pad region 103 and covers the contact pad ration103.

In accordance with the first embodiment, the first portion 101 d of thepassivation layer stack 101 corresponds to those portions of the secondpassivation layer 101 b and the third passivation layer 101 c that arelocated above the contact pad region 103, and the second portion 101 eof the passivation layer stack 101 corresponds to that portion of thefirst passivation layer 101 a that is located on the contact pad region103 or, more precisely, on the upper surface 103 a of the contact padregion 103. Hence, by removing the portions of the second and thirdpassivation layer 101 b, 101 c that are located above the contact padregion 103, the underlying portion of the first passivation layer 101 ais exposed.

In accordance with an embodiment, the first portion 101 d of thepassivation layer stack 101 may be removed by means of an etch process.For this purpose, in accordance with one embodiment, a photoresist layer(not shown in FIG. 1B), i.e., a layer comprising a photoresist material,may be deposited on the third passivation layer 101 c (for example, onthe uppermost silicon nitride layer in accordance with an embodiment).Subsequently, the photoresist layer may be patterned such that materialof the photoresist layer is removed from above the contact pad region103.

A photoresist layer, which is patterned in the way described above,clearly may serve as a photoresist mask during the etching of the secondand third passivation layer 101 b, 101 c. The photoresist layer may, forexample, be patterned by means of a conventional lithographical processor by any other suitable process.

In accordance with one embodiment, the second passivation layer 101 band the third passivation layer 101 c may be etched away from above thecontact pad region 103 by means of a reactive ion etch (RIE) process. Inaccordance with other embodiments, the second and third passivationlayers 101 b, 101 c may be etched using any other suitable etchingprocess.

Clearly, by means of the etching process, the third passivation layer101 c (for example, the uppermost silicon nitride layer) and the secondpassivation layer 101 b (for example, the silicon oxide layer) areopened above the contact pad region 103 (in other words, above the pad).The first passivation layer 101 a (for example, the lowermost siliconnitride layer in accordance with an embodiment) may serve as an etchstop layer during the etching of the second passivation layer 101 b andthe third passivation layer 101 c. In other words, the etching of thesecond and third passivation layers 101 b, 101 c may stop on the firstpassivation layer 101 a (for example, on the lowermost silicon nitridelayer in accordance with an embodiment) such that the contact pad region103 (for example, the copper pad) remains completely covered by thefirst passivation layer 101 a. Thus, the contact pad region 103 may beprotected against possible subsequent aggressive process steps by meansof the first passivation layer 101 a (for example, the lowermost siliconnitride layer in accordance with an embodiment), as described hereinbelow.

After etching the second passivation layer 101 b and the thirdpassivation layer 101 c of the passivation layer stack 101, theremaining material of the photoresist layer may be removed, for example,using an oxygen plasma or wet chemistry (e.g., using a wet chemical etchprocess) in accordance with an embodiment. Alternatively, thephotoresist layer or photoresist mask may be removed by means of in-situresist ashing in accordance with an embodiment.

Clearly, by means of the etching of the second passivation layer 101 band the third passivation layer 101 c, a recess 107 is formed within thepassivation layer stack 101 above the contact pad region 103, whereinthe bottom surface of the recess 107 is formed by the exposed portion ofthe first passivation layer 101 a (for example, of the lowermost siliconnitride layer in accordance with an embodiment).

The first passivation layer 101 a covers the contact pad region 103(e.g., the copper pad 103) and may thus protect the contact pad region103 against aggressive or harsh process steps such as, for example,aggressive etching process steps, e.g., against an etching process thatmay be used to remove the remaining material of the photoresist layerfrom above the passivation layer stack 101.

In this connection, it is noted that the contact pad region 103 or, moreprecisely, the upper surface 103 a of the contact pad region 103, mayhave, in principle, an arbitrary shape, for example, a rectangularshape, a quadratic shape, a hexagonal shape, an octagonal shape, acircular shape, etc.

In one embodiment, a lateral dimension or diameter of the contact padregion 103, which corresponds to a diameter of the recess 107 or opening107, may be approximately 40 μm to 180 μm, although in other embodimentsthe opening 107 and/or the contact pad region 103 may have other lateraldimensions.

Furthermore, as FIG. 1B only shows a cross-sectional view of theintegrated circuit element 150, it is noted that in addition to thecontact pad region 103 shown in FIG. 1B, other contact pad regions maybe formed within the surface region 102 of the integrated circuitelement 150, and clearly be located “in front of” or “behind” thesurface plane shown in FIG. 1B. These additional contact pad regions mayin each case be connected to the metallization region 105 (e.g., to theconductive line 105) by means of respective contact holes (vias), andmay further be processed in a similar manner and/or in parallel to theprocessing of the contact pad region 103 shown in FIG. 1B.

FIG. 1C shows another processing stage 140 of the method ofmanufacturing a contact pad in accordance with the first embodiment ofthe invention. It is shown the formation and patterning of an adhesionlayer 108.

The adhesion layer 108 is formed on the passivation layer stack 101,that is, on the remaining portions of the third passivation layer 101 c(for example, of the uppermost silicon nitride layer in accordance withan embodiment), and on the exposed portion of the upper surface of thefirst passivation layer 101 a.

In accordance with one embodiment, the adhesion layer 108 is formed bydeposition of an imide layer onto the passivation layer stack 101. Theimide layer may include an arbitrary imide material, for example anarbitrary photoimide or polyimide material in accordance with anembodiment. In accordance with alternative embodiments, in principle,any material that may be structured or patterned by means of aphotolithographical process, or any material that resists a plasmaetching process, may be used for the adhesion layer. For example, othersuitable resist materials may be used.

The adhesion layer 108 (for example, the photoimide layer) may bedeposited on the passivation layer stack 101 using a spin-on process inaccordance with one embodiment. In accordance with another embodiment, avapor deposition process such as, for example, a CVD process may be usedto deposit the adhesion layer 108. In accordance with other embodiments,other suitable deposition processes may be used to deposit the adhesionlayer 108.

In some embodiments, the adhesion layer 108 is formed such that it has athickness in the range from about 1 μm to about 50 μm, for example, inthe range from about 3 μm to about 20 μm, e.g., 20 μm in one embodiment.

The deposition of the layer 108 (e.g., of the imide layer) furtherincludes depositing the layer 108 onto the exposed portion of the uppersurface of the first passivation layer 101 a (for example, of the firstsilicon nitride layer).

The layer 108 is patterned, for example, by means of aphotolithographical process in accordance with an embodiment. In thepatterning of the adhesion layer 108, the adhesion layer 108 is removedfrom above the contact pad region 103 or, more precisely, from above theportion of the first passivation layer 101 a that covers the contact padregion 103.

In the embodiment shown in FIG. 1C, the patterning of the adhesion layer108 further includes removing the adhesion layer 108 from above a thirdportion 101 f and a fourth portion 101 g of the passivation layer stack101 located proximate the contact pad region 103, such that lateralspacings 109 a, 109 b are formed between edges 108 a, 108 b of theadhesion layer 108 and edges 103 b, 103 c of the contact pad region 103as shown in FIG. 1C. In other words, the adhesion layer 108 is patternedin such a way that a first edge 108 a of the adhesion layer 108 ispulled back from a first edge 103 b of the contact pad region 103, and asecond edge 108 b of the adhesion layer 108 is pulled back from a secondedge 103 c of the contact pad region 103.

The lateral spacings 109 a, 109 b between the adhesion layer 108 (forexample, the imide layer) and the contact pad region 103 may have adimension of approximately about 1 μm to about 10 μm, for example about3 μm to about 8 μm, e.g., about 5 μm in one embodiment.

Clearly, in accordance with the embodiment shown in FIG. 1C the edges108 a, 108 b of the patterned adhesion layer 108 are displaced orshifted by respective spacings 109 a, 109 b with respect to the innersidewalls of the recess 107, in other words with respect to the edges103 b, 103 c of the contact pad region 103. One effect of pulling backthe edges 108 a, 108 b of the adhesion layer 108 from the contact pad103 is that a contact or reaction of the material of the adhesion layer108 (for example, the imide material) with the material of the contactpad region 103 (for example, the copper material of a copper pad) may beavoided.

For example, an imide material that is used for the adhesion layer 108clearly “works”, and by means of shifting the edges 108 a, 108 b of theadhesion layer 108 away from the contact pad region 103, a contact ofthe imide material of the adhesion layer 108 with the contact pad region103 is avoided. In other words, an alignment of the adhesion layer or ofthe edges 108 a, 108 b of the adhesion layer 108 with the edge(s) of thecontact pad 103 can be avoided. For this reason, also materials whichare not compatible with copper (for example, materials which react withcopper) may be used as material for the adhesion layer 108. For example,arbitrary imides, and in particular photoimides that are not compatiblewith copper, may be used as material for the adhesion layer 108.

In the deposition of an imide layer as adhesion layer 108, thedeposition of very thin imides is possible as the imide material remainshomogeneous during the deposition.

In one embodiment, a post-treatment of the adhesion layer 108 (forexample, of the imide layer) is carried out. The post-treatment mayinclude a cyclization of the photoimide material by means of anannealing step and a subsequent oxygen plasma treatment. The temperingor annealing step may include a tempering or heating of the adhesionlayer 108 within an inert gas atmosphere such as, for example, anitrogen (N₂) atmosphere, a forming gas atmosphere, or a noble gas(e.g., Ar) atmosphere, for example up to a temperature of approximatelyabout 350° C. to about 450° C., in accordance with embodiments of theinvention.

In one embodiment, the cyclizated photoimide material may bepost-treated using an oxygen plasma. In this connection, it is notedthat the material of the contact pad region 103 (for example, the coppermaterial of a copper contact pad) normally would be oxidized in anoxygen plasma environment. However, in accordance with embodiments ofthe invention, the upper surface 103 a of the contact pad region 103 iscovered by the first passivation layer 101 a and thus protected againstaggressive process steps such as the oxygen plasma post treatment step.

With respect to the patterning of the adhesion layer 108, and inparticular with respect to the dimension of the lateral spacings 109 a,109 b between the adhesion layer 108 and the contact pad region 103, itis noted that additional contact pad regions (not shown in FIG. 1C) maybe formed within the substrate or, more precisely, within the surfaceregion 102 of the integrated circuit element 150 at some distance fromthe contact pad region 103 shown in FIG. 1C, and the adhesion layer 108may clearly be formed on portions of the passivation layer stack 101disposed between two or more contact pad regions, and the lateralspacings 109 a, 109 b may have such a lateral dimension that clearly theportions of the adhesion layer 108 disposed between two or more contactpad regions have a sufficient width or length and thus a sufficientmechanical or structural stability.

FIG. 1D shows another processing stage 160 of the method ofmanufacturing a contact pad in accordance with the first embodiment ofthe invention. It is shown the removal of the second portion 101 e ofthe passivation layer stack 101 from above the contact pad region 103.In accordance with the first embodiment, the removal of the secondportion of the passivation layer stack 101 corresponds to the removal ofthat portion of the first passivation layer 101 a that covers thecontact pad region 103 from above the upper surface 103 a of the contactpad region 103, thereby exposing the upper surface 103 a of the contactpad region 103.

In accordance with one embodiment, the first passivation layer 101 a isremoved from the upper surface 103 a of the contact pad region 103 bymeans of a reactive ion etch (RIE) process. In alternative embodiments,other suitable processes, for example, other suitable etch processes,may be used to remove the first passivation layer 101 a from the uppersurface 103 a of the contact pad region 103. In accordance with oneembodiment, the first passivation layer 101 a (e.g., the lowermostsilicon nitride layer) is etched away from the upper surface 103 a ofthe contact pad region 103 using the second and third passivation layer101 b, 101 c (e.g., the silicon oxide layer and the uppermost siliconnitride layer) of the passivation layer stack 101 as a hard mask. Inother words, in accordance with an embodiment, the second portion of thepassivation layer stack 101 (for example, the lowermost silicon nitridelayer) that covers the contact pad region 103 is opened by means of anetching step using the second passivation layer 101 b and the thirdpassivation layer 101 c (for example, the SiO₂/SiN_(x) double layer) asa hard mask.

Clearly, by means of the removal of the second portion of thepassivation layer stack 101 (that is, by means of removing the portionof the first passivation layer 101 a located on the contact pad region103), the upper surface 103 a of the contact pad region 103 is exposed.

In accordance with the first embodiment, in the removal process of thesecond portion 101 e of the passivation layer stack 101 (for example, inthe etching of the portion of the first passivation layer 101 a coveringthe contact pad region 103), also an upper portion of the third portion101 f and an upper portion of the fourth portion 101 g of thepassivation layer stack 101 are removed, such that a first step 110 aand a second step 110 b are formed within the third passivation layer101 c, as can be seen in FIG. 1D. In other words, during the removal ofthe first passivation layer 101 a from above the upper surface 103 a ofthe contact pad region 103, the third passivation layer 101 c is thinnedin those regions where it is not covered by the adhesion layer 108.

In this connection it is noted that in accordance with some embodimentsthe first passivation layer 101 a (for example, the first siliconnitride layer) may have a rather small thickness, for example, down toabout 20 nm in accordance with an embodiment, such that an etchingprocess, which may be used to remove the first passivation layer 101 afrom the upper surface 103 a of the contact pad region 103, may beapplied for a comparatively short time. This has the effect that in theetching of the first passivation layer 101 a the exposed portions of thethird passivation layer 101 c (e.g., of the second silicon nitridelayer) and furthermore of the adhesion layer 108 are thinned only veryslightly. In other words, since the removal of the first passivationlayer 101 a from the upper surface 103 a of the contact pad region 103may only take a short time, only very little material is removed fromthe third passivation layer 101 c and/or from the adhesion layer 108.

In some embodiments, one or more cleaning steps such as, for example, apolymer removal step or a copper surface cleaning step, may be carriedout after the removal of the second portion of the passivation layerstack 101.

FIG. 1E shows another processing stage 180 of the method ofmanufacturing a contact pad in accordance with the first embodiment ofthe invention. It is shown the formation of a reinforcement layer stack111 on the contact pad region 103. The reinforcement layer stack 111includes a first reinforcement layer 111 a formed on the upper surface103 a of the contact pad region 103, a second reinforcement layer 111 bformed on the first reinforcement layer 111 a, and a third reinforcementlayer 111 c formed on the second reinforcement layer 111 b.

In some embodiments, at least one of the first, second or thirdreinforcement layers are formed by means of a deposition process. Inaccordance with one embodiment, at least one of the first, second orthird reinforcement layers are deposited by means of an electrolessplating process. By means of electroless plating, the pad reinforcementlayer stack 111 may, for example, be deposited selectively onto thecontact pad region 103, for example, selectively onto a copper contactpad.

In accordance with an embodiment, the first reinforcement layer 111 aincludes or is made of nickel (Ni) and/or nickel phosphorous (Ni₃P). Inaccordance with other embodiments, the first reinforcement layer 111 amay include or may be made of other materials or material systems suchas, for example, a binary material including nickel, a ternarystress-accommodated material, for example, nickel boron (NiB), NiWP,NiMoP, CoWP, or other materials or material systems.

In accordance with some embodiments, the first reinforcement layer 111 ahas a thickness in the range from about 500 nm to about 10 μm, forexample, in the range from about 500 nm to about 3 μm, e.g., 1 μm in oneembodiment. The first reinforcement layer 111 a may serve to increasethe stability of the contact pad.

In accordance with one embodiment, the second reinforcement layer 111 bincludes or is made of palladium (Pd). In accordance with alternativeembodiments, the second reinforcement layer 111 b may include or may bemade of other materials or material systems such as, for example,platinum (Pt), copper (Cu), silver (Ag). The second reinforcement layer111 b is an optional layer and may have a thickness in the range fromabout 0 to about 1 μm, for example, in the range from about 50 μm toabout 500 nm, e.g., 300 nm in one embodiment.

In accordance with one embodiment, the third reinforcement layer 111 cis made of gold (Au). In accordance with alternative embodiments, thethird reinforcement layer 111 c may include or may be made of othermaterials or material systems such as, for example, platinum (Pt). Thethird reinforcement layer 111 c is also an optional layer and may have athickness in the range from about 0 to about 200 nm, for example, in therange from about 20 nm to about 100 nm, e.g., 50 nm in accordance withan embodiment.

In accordance with some embodiments, the thicknesses of the optionalsecond reinforcement layer 111 b and of the optional third reinforcementlayer 111 c may be adapted or optimized for a particular bondingapplication.

In accordance with the first embodiment shown in FIG. 1E, the totalthickness of the reinforcement layer stack 111 (that is, the addedthicknesses of the first reinforcement layer 111 a, second reinforcementlayer 111 b and third reinforcement layer 111 c) is such that the uppersurface of the reinforcement layer stack 111 (or, more precisely, theupper surface of the third reinforcement layer 111 c) is flush (in otherwords, co-planar) with the upper surface of the exposed third portion101 f and fourth portion 101 g of the passivation layer stack 101.However, in other embodiments, the upper surface of the reinforcementlayer stack 111 may be located lower or higher than the upper surface ofthe passivation layer stack 101 or, more precisely, than the uppersurfaces of the exposed portions 101 f, 101 g of the passivation layerstack 101.

In accordance with the embodiment shown in FIG. 1E, the thirdreinforcement layer 111 c of the reinforcement layer stack 111 (forexample, the gold layer) is not in contact with the adhesion layer 108.Furthermore, the third portion 101 f and the fourth portion 101 g of thepassivation layer stack 101, which are located proximate the contact padregion 103, are free from the adhesion layer 108 (for example, free fromthe imide layer). In these regions 101 f, 101 g, the thickness of thethird passivation layer 101 c is smaller than in those regions of thepassivation layer stack 101 that are covered by the adhesion layer 108.Clearly, the third passivation layer 101 c has a first step 110 alocated in the third portion 101 f of the passivation layer stack 101,and a second step 110 b located in the fourth portion 101 g of thepassivation layer stack 101, wherein the first and second steps 110 a,110 b are a result of the second pad opening step, that is, the removalof the second portion 101 e of the passivation layer stack 101 (forexample, the etching of the downmost silicon nitride layer) described inconnection with FIG. 1D herein above.

Clearly, the method in accordance with the first embodiment of theinvention, as described herein above in connection with FIG. 1A to FIG.1E, includes a two-stage etching of a three-layer passivation layerstack, wherein a contact pad region is protected against aggressiveprocessing steps such as, for example, aggressive etching steps, bymeans of the lowermost of the three passivation layers of thepassivation layer stack, and furthermore includes the formation of areinforcement layer stack directly onto the contact pad region.

Furthermore, FIG. 1E clearly shows an integrated circuit element 150 inaccordance with an embodiment of the invention. The integrated circuitelement 150 includes a substrate, a surface region 102 of the substrateincluding a contact pad region 103. Furthermore, the integrated circuitelement 150 includes a passivation layer stack 101 formed on the surfaceregion 102 and adjacent to the contact pad region 103. The passivationlayer stack 101 includes a first passivation layer 101 a formed on thesurface region 102, a second passivation layer 101 b formed on the firstpassivation layer 101 a, and a third passivation layer 111 c formed onthe second passivation layer 101 b. In a portion 101 f and a portion 101g of the passivation layer stack 101 proximate the contact pad region103, an upper portion of the passivation layer stack 101 is removed. Theintegrated circuit element 150 further includes an adhesion layer 108formed on the passivation layer stack 101. In the portions 101 f and 101g of the passivation layer stack 101, the passivation layer stack 101 isfree from the adhesion layer 108. The integrated circuit element 150further includes a reinforcement layer stack 111 formed on an uppersurface 103 a of the contact pad region 103. The reinforcement layerstack 111 includes a first reinforcement layer 111 a formed on the uppersurface 103 a of the contact pad region 103, a second reinforcementlayer 111 b formed on the first reinforcement layer 111 a, and a thirdreinforcement layer 111 c formed on the second reinforcement layer 111b. The upper surface of the reinforcement layer stack 111 is flush withthe upper surface of the passivation layer stack 101 or, more precisely,with the upper surface of the third passivation layer 101 c within theportions 111 f, 111 g of the passivation layer stack 101.

In the following, various processing stages of a method of manufacturinga contact pad of an integrated circuit element in accordance with asecond embodiment of the present invention are described with respect toFIG. 2A to FIG. 2E. The individual processing stages are to some extentsimilar to those of the method of manufacturing a contact pad inaccordance with the first embodiment of the invention, described hereinabove in connection with FIG. 1A to FIG. 1E, the main difference of themethod according to the second embodiment being that a passivation layerstack is formed which includes only two passivation layers, as describedherein below.

For the interest of brevity, elements and/or steps that are similar oridentical to those described in connection with method according to thefirst embodiment, will not be re-described in detail. Instead, referenceis made to the description given above in connection with FIG. 1A toFIG. 1E.

FIG. 2A shows a processing stage 200 of the method of manufacturing acontact pad in accordance with the second embodiment of the invention.Similarly to FIG. 1A, it is shown the formation of a passivation layerstack 201 on an upper surface of a surface region 102 of an integratedcircuit element 150, the surface region 102 including a contact padregion 103. In accordance with the second embodiment, the passivationlayer stack 201 includes a first passivation layer 201 a formed on theupper surface 102 a of the surface region 102, and a second passivationlayer 201 b formed on the first passivation layer 201 a.

The passivation layer stack 201 further includes a first portion 201 dand a second portion 201 e. In accordance with the second embodiment,the second portion 201 e of the passivation layer stack 201 correspondsto a portion of the first passivation layer 201 a that is formed on theupper surface 103 a of the contact pad region 103, and the first portion201 d corresponds to a portion of the second passivation layer 201 bthat is formed on the second portion 201 e of the passivation layerstack 201.

In accordance with an embodiment, at least one of the first passivationlayer 201 a and the second passivation layer 201 b may be formed by adeposition process, for example, a CVD process such as, for example,PECVD. However, in alternative embodiments, the formation of the firstpassivation layer 201 a and/or of the second passivation layer 201 b maybe achieved by other suitable deposition methods.

In one embodiment, the first passivation layer 201 a is formed as asilicon nitride (SiN_(x)) layer, and the second passivation layer 201 bis formed as a silicon oxide (SiO₂) layer. However, in alternativeembodiments the first passivation layer 201 a and/or the secondpassivation layer 201 b may include or may be made of other materials.For example, in one embodiment, the second passivation layer 201 b maybe formed as a silicon carbide (SiC) layer.

In some embodiments, the thicknesses of the first passivation layer 201a and the second passivation layer 201 b are chosen such that thethickness of the second passivation layer 201 b is considerably greaterthan the thickness of the first passivation layer 201 a. In accordancewith an embodiment, the first passivation layer 201 a (for example, thesilicon nitride layer) and/or the second passivation layer 201 b (forexample, the silicon oxide layer) may have similar thicknesses asdescribed for the first and second passivation layer of the passivationlayer stack 101 of the first embodiment.

FIG. 2B shows another processing stage 220 of the method ofmanufacturing a contact pad in accordance with the second embodiment ofthe invention. Similarly to FIG. 1B, it is shown the removal of thefirst portion 201 d of the passivation layer stack 201 from above thecontact pad region 103, wherein the second portion 201 e of thepassivation layer stack 201 remains on the contact pad region 103 andcovers the contact pad region 103. In accordance with the secondembodiment, the removal of the first portion 201 d of the passivationlayer stack 201 corresponds to the removal of the second passivationlayer 201 b (for example, the silicon oxide layer) from above thecontact pad region 103 such that the portion of the first passivationlayer 201 a (for example, the silicon nitride layer) that is located onthe contact pad region 103, is exposed.

Clearly, by removing the first portion 201 d of the passivation layerstack 201, a recess 207 is formed above the contact pad region 103, withthe bottom surface of the recess 207 being formed by the exposed portionof the first passivation layer 201 a. The removal of the first portion201 d of the passivation layer stack 201, that is the removal of thesecond passivation layer 201 b from above the contact pad region 103,may be achieved by means of an etching process similar to the etching ofthe second and/or third passivation layer of the passivation layer stack101 described herein above in connection with FIG. 1B.

In the method in accordance with the second embodiment, the firstpassivation layer 201 a (for example, the silicon nitride layer) mayserve as an etch stop layer when etching the second passivation layer201 b (for example, the silicon oxide layer). Similarly to the firstembodiment described in connection with FIG. 1B, the first passivationlayer 201 a remains on the contact pad region 103 and covers the contactpad region 103 so that the contact pad region 103 may be protectedagainst subsequent aggressive processing steps as described herein abovein connection with the first embodiment.

FIG. 2C shows another processing stage 240 of the method ofmanufacturing a contact pad in accordance with the second embodiment ofthe invention. Similarly to FIG. 1C, it is shown the formation of anadhesion layer 108 on the passivation layer stack 201, and thepatterning of the adhesion layer 108, wherein the adhesion layer 108 isremoved from at least above the contact pad region 103. The formationand the patterning of the adhesion layer 108 may be achieved in asimilar manner as described herein above in connection with FIG. 1C.

In accordance with the second embodiment, the adhesion layer 108 ispulled back from the edges 103 b, 103 c of the contact pad region 103such that a first spacing 109 a is formed between the first edge 108 aof the adhesion layer 108 and the first edge 103 b of the contact padregion 103, and a second spacing 109 b is formed between the second edge108 b of the adhesion layer 108 and the second edge 103 c of the contactpad region 103. Thus, a third portion 201 f and a fourth portion 201 gof the passivation layer stack 201 are free from the adhesion layer 108.In other words, an upper surface of the second passivation layer 201 bis exposed within the portions 201 f and 201 g of the passivation layerstack 201.

In accordance with the second embodiment, the contact pad region 103 isprotected against possible aggressive processing steps, e.g., aggressiveetching steps, which may, for example, occur during the formation and/orpatterning of the adhesion layer 108, by means of the first passivationlayer 201 a covering the contact pad region 103.

FIG. 2D shows another processing stage 260 of the method ofmanufacturing a contact pad in accordance with the second embodiment ofthe invention. Similarly to FIG. 1D, it is shown the removal of thesecond portion 201 e of the passivation layer stack 201 from above thecontact pad region 103. In accordance with the second embodiment, theremoval of the second portion 201 e of the passivation layer stack 201corresponds to the removal of the first passivation layer 201 a fromabove the contact pad region 103, such that the upper surface 103 a ofthe contact pad region 103 is exposed. In other words, the firstpassivation layer 201 a is opened above the contact pad region 103 suchthat the bottom surface of the recess 207 is now formed by the uppersurface 103 a of the contact pad region 103.

In one embodiment, the removal of the second portion 201 e of thepassivation layer stack 201 (that is, the removal of the firstpassivation layer 201 a from above the contact pad region 103) isachieved by means of an etching process, for example, as an etchingprocess as described herein above in connection with FIG. 1B.

Similarly as described herein above in connection with FIG. 1B, an upperportion of the second passivation layer 201 b is removed during theremoval of the first passivation layer 201 a within the portions 201 fand 201 g of the passivation layer stack 201 proximate the contact padregion 103, that is within the portions 201 f, 201 g of the passivationlayer stack 201 that are not covered by the adhesion layer 108. Thus, afirst step 210 a is formed in the second passivation layer 201 b withinthe third portion 201 f of the passivation layer stack 201, and a secondstep 210 b is formed in the passivation layer 201 b within the fourthportion 201 g of the passivation layer stack 201, as shown in FIG. 2Dand similarly to the first embodiment described in connection with FIG.1D.

FIG. 2E shows another processing stage 280 of the method ofmanufacturing a contact pad in accordance with the second embodiment ofthe invention. Similarly to FIG. 1E, it is shown the formation of areinforcement layer stack 111 on the contact pad region 103 after theremoval of the second portion 201 e of the passivation layer stack 201.The reinforcement layer stack 111 includes a first reinforcement layer111 a, a second reinforcement layer 111 b and a third reinforcementlayer 111 c, which may be configured and/or formed in a similar manneras described herein above for the first embodiment in connection withFIG. 1E.

Although it is shown that the reinforcement layer stack 111 includesthree reinforcement layers 111 a, 111 b, and 111 c, it is to beunderstood that the reinforcement layer stack 111 may alternativelyinclude a different number of reinforcement layers as described hereinabove in connection with FIG. 1E.

Furthermore, it is shown in FIG. 2E that the upper surface of thereinforcement layer stack 111 (that is, the upper surface of the thirdreinforcement layer 111 c) is flush with the upper surface of thepassivation layer stack 201 or, more precisely, with the upper surfacesof the third and fourth portion 201 f, 201 g of the passivation layerstack 201. However, as described herein above, the upper surface of thereinforcement layer stack 111 may also be located lower or higher thanthe upper surface of the passivation layer stack 201. The number ofreinforcement layers and/or the material of the individual reinforcementlayers of the reinforcement layer stack 111 may be adapted to aparticular bonding application as mentioned above in connection with thefirst embodiment.

Clearly, the method in accordance with the second embodiment of theinvention, as described herein above in connection with FIG. 2A to FIG.2E, includes a two-stage etching of a two-layer passivation layer stack,wherein a contact pad region is protected against aggressive processingsteps such as, for example, aggressive etching steps, by means of thelower one of the two passivation layers of the passivation layer stack,and furthermore includes the formation of a reinforcement layer stackdirectly onto the contact pad region.

Furthermore, FIG. 2E clearly shows an integrated circuit element 150 inaccordance with an embodiment of the invention. The integrated circuitelement 150 includes a substrate, a surface region 102 of the substrateincluding a contact pad region 103. Furthermore, the integrated circuitelement 150 includes a passivation layer stack 201 formed on the surfaceregion 102 and adjacent to the contact pad region 103. The passivationlayer stack 201 includes a first passivation layer 201 a formed on thesurface region 102, and a second passivation layer 201 b formed on thefirst passivation layer 201 a. In a portion 201 f and a portion 201 g ofthe passivation layer stack 201 proximate the contact pad region 103, anupper portion of the passivation layer stack 201 is removed. Theintegrated circuit element 150 further includes an adhesion layer 108formed on the passivation layer stack 201. In the portions 201 f and 201g of the passivation layer stack 201, the passivation layer stack 201 isfree from the adhesion layer 108. The integrated circuit 150 furtherincludes a reinforcement layer stack 111 formed on an upper surface 103a of the contact pad region 103. The reinforcement layer stack 111includes a first reinforcement layer 111 a formed on the upper surface103 a of the contact pad region 103, a second reinforcement layer 111 bformed on the first reinforcement layer 111 a, and a third reinforcementlayer 111 c formed on the second reinforcement layer 111 b. The uppersurface of the reinforcement layer stack 111 is flush with the uppersurface of the passivation layer stack 201 or, more precisely, with theupper surface of the second passivation layer 201 b within the portions201 f, 201 g of the passivation layer stack 201.

In the following, various processing stages of a method of manufacturinga contact pad of an integrated circuit element in accordance with athird embodiment of the invention are described with respect to FIG. 3Ato FIG. 3E. The individual processing stages are to some extent similarto those of the methods of manufacturing a contact pad in accordancewith the first or second embodiment of the invention, described hereinabove in connection with FIG. 1A to FIG. 2E, the main difference of themethod according to the third embodiment being that a passivation layerstack is formed which includes only one passivation layer, as describedherein below.

For the interest of brevity, elements and/or steps that are similar oridentical to those described in connection with the method according tothe first or second embodiment will not be re-described in detail.Reference is made to the description given above in connection with FIG.1A to FIG. 2E.

FIG. 3A shows a processing stage 300 of the method of manufacturing acontact pad in accordance with the third embodiment of the invention.Similarly to FIG. 1A and FIG. 2A, it is shown the formation of apassivation layer stack 301 on an upper surface of a surface region 102of an integrated circuit element 150, the surface region 102 including acontact pad region 103. The passivation layer stack 301 includes apassivation layer 301 a formed on the upper surface of the surfaceregion 102.

The passivation layer stack 301 further includes a first portion 301 dand a second portion 301 e. In accordance with the third embodiment, thesecond portion 301 e of the passivation layer stack 301 corresponds to aportion of the passivation layer 301 a that is formed on an uppersurface 103 a of the contact pad region 103, and the first portion 301 dcorresponds to a portion of the passivation layer 301 a that is formedon the second portion 301 e of the passivation layer stack 301.

The passivation layer 301 a is formed on the upper surface 103 a of thecontact pad region 103 and on the upper surface of an insulating layer102 c formed within the surface region 102.

In one embodiment, the passivation layer 301 a is formed as a siliconnitride (SiN_(x)) layer. However, in accordance with other embodiments,the passivation layer 301 a may include or may be made of othermaterials.

In some embodiments, the passivation layer 301 a (for example, thesilicon nitride layer) is formed by means of a vapor deposition processsuch as, for example, a CVD process, e.g., PECVD. However, in accordancewith other embodiments, the passivation layer 301 a may be formed byother suitable techniques.

The passivation layer 301 a may have a thickness in the range from about30 nm to about 4 μm, for example, in the range from about 40 nm to about2 μm, e.g., 1 μm in one embodiment.

FIG. 3B shows another processing stage 320 of the method ofmanufacturing a contact pad in accordance with the third embodiment ofthe invention. Similarly to FIG. 1B and FIG. 2B, it is shown the removalof the first portion 301 d of the passivation layer stack 301 from abovethe contact pad region 103, wherein the second portion 301 e of thepassivation layer stack 301 remains on the contact pad region 103 andcovers the contact pad region 103.

In accordance with the third embodiment, the removal of the firstportion 301 d of the passivation layer stack 301 corresponds to removingan upper portion of the passivation layer 301 a (for example, of thesilicon nitride layer) from above the contact pad region 103, wherein a(thin) lower portion of the passivation layer 301 a (for example, of thesilicon nitride layer) remains on the contact pad region 103 and coversthe contact pad region 103. Thus, after removing the first portion 301 dof the passivation layer stack 301, the passivation layer 301 a has asmall thickness in a region above the contact pad region 103 (forexample, in some embodiments, a thickness which is approximately thesame as the thickness of the first passivation layer 101 a shown in FIG.1A), and has a greater thickness in those regions of the passivationlayer stack 301 that are not located above the contact pad region 103(or above any other additional contact pad region not shown in FIG. 3B).

In one embodiment, the removal of the first portion 301 d of thepassivation layer stack 301 is achieved by means of an etching processin a similar manner as described herein above in connection with thefirst or second embodiment. In this connection, it is noted that, inaccordance with one embodiment, the etching process that may be used toremove the first portion 301 d of the passivation layer stack 301 may beconfigured as an etch process with a predetermined fixed time duration.Clearly, the etching time of the etch process may be chosen in such away that a thin portion (i.e., the second portion 301 e) of thepassivation layer 301 a remains on the contact pad region 103 after theetching of the first portion 301 d of the passivation layer stack 301 iscompleted. In other words, in accordance with the third embodiment, theetch stop of the etching process may be defined by a predeterminedetching time, whereas in accordance with the first and the secondembodiment the etch stop may, for example, be achieved by means of thelowermost passivation layer of the passivation layer stack serving as anetch stop layer.

Clearly, by removing the first portion 301 d of the passivation layerstack 301, a recess 307 is formed above the contact pad region 103, withthe bottom surface of the recess 307 being formed by the upper surfaceof the second portion 301 e of the passivation layer stack 301.

FIG. 3C shows another processing stage 340 of the method ofmanufacturing a contact pad in accordance with the third embodiment ofthe invention. Similarly to FIG. 1C and FIG. 2C it is shown theformation of an adhesion layer 108 on the passivation layer stack 301,and the patterning of the adhesion layer 108, wherein the adhesion layer108 is removed from at least above the contact pad region 103. Theformation and/or patterning of the adhesion layer 108 may be achieved ina similar manner as described herein above in connection with themethods according to the first or second embodiment.

In accordance with the third embodiment and similar to the first andsecond embodiment, the adhesion layer 108 is patterned in such a way,that a third portion 301 f and a fourth portion 301 g of the passivationlayer stack 301 proximate the contact pad region 103 are free from theadhesion layer 108. In other words, the edges 108 a, 108 b of thepatterned adhesion layer 108 are pulled back such that spacings 109 a,109 b are formed between the edges 108 a, 108 b of the adhesion layer108 and the edges 103 a, 103 b of the contact pad region 103 as shown inFIG. 3C and described herein above in connection with the methodsaccording to the first embodiment and the second embodiment.

FIG. 3D shows another processing stage 360 of the method ofmanufacturing a contact pad in accordance with the third embodiment ofthe invention. Similarly to FIG. 1D and FIG. 2D, it is shown the removalof the second portion 301 e of the passivation layer stack 301 fromabove the contact pad region 103. In accordance with the thirdembodiment, the removal of the second portion 301 e of the passivationlayer stack 301 corresponds to the removal of the thin portion of thepassivation layer 301 a (for example, of the silicon nitride layer)located above the contact pad region 103.

By removing the second portion 301 e of the passivation layer stack 301from above the contact pad region 103, the upper surface 103 a of thecontact pad region 103 is exposed.

In one embodiment, the removal of the second portion 301 e of thepassivation layer stack 301 is achieved by means of an etching processas described herein above in connection with the first embodiment andthe second embodiment. In this connection, it is noted that during theetching of the second portion 301 e of the passivation layer stack 301also an upper portion of the third portion 301 f and an upper portion ofthe fourth portion 301 g of the passivation layer stack 301 locatedproximate the contact pad region 103 are removed, thereby forming steps310 a, 310 b within the passivation layer 301 a in the portions 301 f,301 g of the passivation layer stack 301 as can be seen in FIG. 3D andas is also described herein above in connection with the firstembodiment and the second embodiment.

FIG. 3E shows another processing stage 380 of the method ofmanufacturing a contact pad in accordance with the third embodiment ofthe invention. Similarly to FIG. 1E and FIG. 2E it is shown theformation of a reinforcement layer stack 111 on the contact pad region103 after removal of the second portion 301 e of the passivation layerstack 301 (that is, after the removal of the thin portion of thepassivation layer 301 a located on the contact pad region 103).

The reinforcement layer stack includes three reinforcement layers 111 a,111 b and 111 c, and may be formed in a similar manner as describedherein above in connection with the first and second embodiment. Inaccordance with the third embodiment, the upper surface of thereinforcement layer stack 111 is flush with the upper surface of thepassivation layer stack 301 or, more precisely, with the upper surfaceof the portions 301 f and 301 g of the passivation layer stack 301located proximate the contact pad region 103.

In accordance with other embodiments, the reinforcement layer stack 111may include a different number of reinforcement layers and/or the uppersurface of the reinforcement layer stack 111 may be located lower orhigher than the upper surface of the passivation layer stack 301. Inprinciple, as described before in connection with the first and secondembodiments of the invention, the number of reinforcement layers in thereinforcement layer stack 111 and/or the materials of the individualreinforcement layers may be chosen or adapted with respect to aparticular bonding application.

Clearly, the method of manufacturing a contact pad in accordance withthe third embodiment, as described herein above in connection with FIG.3A to FIG. 3E, includes a two-stage etching of a passivation layer,wherein in a first etching stage an upper portion of the passivationlayer is removed leaving a thin lower portion on the contact pad regionand covering the contact pad region. Thus, the contact pad region may beprotected against aggressive processing steps (such as, for example,aggressive etching steps) involved, for example, in the formation and/orpatterning of an adhesion layer formed on the passivation layer stack.In a second stage, the thin portion of the passivation layer is removedsuch that the contact pad region is exposed. Furthermore, in accordancewith the third embodiment, a reinforcement layer stack is formeddirectly on the contact pad region.

Furthermore, FIG. 3E clearly shows an integrated circuit element 150 inaccordance with an embodiment of the invention. The integrated circuitelement 150 includes a substrate, a surface region 102 of the substrateincluding a contact pad region 103. Furthermore, the integrated circuitelement 150 includes a passivation layer stack 301 formed on the surfaceregion 102 and adjacent to the contact pad region 103. The passivationlayer stack 301 includes a passivation layer 301 a formed on the surfaceregion 102. In a portion 301 f and a portion 301 g of the passivationlayer stack 301 proximate the contact pad region 103, an upper portionof the passivation layer stack 301 is removed. The integrated circuitelement 150 further includes an adhesion layer 108 formed on thepassivation layer stack 301. In the portions 301 f and 301 g of thepassivation layer stack 301, the passivation layer stack 301 is freefrom the adhesion layer 108. The integrated circuit 150 further includesa reinforcement layer stack 111 formed on an upper surface 103 a of thecontact pad region 103. The reinforcement layer stack 111 includes afirst reinforcement layer 111 a formed on the upper surface 103 a of thecontact pad region 103, a second reinforcement layer 111 b formed on thefirst reinforcement layer 11 a, and a third reinforcement layer 111 cformed on the second reinforcement layer 111 b. The upper surface of thereinforcement layer stack 111 is flush with the upper surface of thepassivation layer stack 301 or, more precisely, with the upper surfaceof the passivation layer 301 a within the portions 301 f, 301 g of thepassivation layer stack 301.

FIG. 4 shows a diagram 400 that illustrates a method of processing acontact pad in accordance with an embodiment of the invention.

In 402, a passivation layer stack is formed on at least an upper surfaceof a contact pad region, the passivation layer stack including at leastone passivation layer. The passivation layer stack may be formed inaccordance with embodiments described herein above.

In 404, a first portion of the passivation layer stack is removed fromabove the contact pad region, wherein a second portion of thepassivation layer stack remains on the contact pad region and covers thecontact pad region. The first portion of the passivation layer stack maybe removed in accordance with one of the embodiments described hereinabove.

In 406, an adhesion layer is formed on the passivation layer stack. Theadhesion layer may be formed in accordance with one of the embodimentsdescribed herein above.

In 408, the adhesion layer is patterned, wherein the adhesion layer isremoved from above the contact pad region. The patterning of theadhesion layer and the removal of the adhesion layer from above thecontact pad region may be achieved in accordance with one of theembodiments described herein above.

In 410, the second portion of the passivation layer stack is removed.The removal of the second portion of the passivation layer stack may beachieved in accordance with one of the embodiments described hereinabove.

In accordance with one embodiment, a reinforcement layer stack is formedon the contact pad region after removing the second portion of thepassivation layer stack, the reinforcement layer stack including atleast one reinforcement layer. In accordance with another embodiment,forming the passivation layer stack includes depositing a firstpassivation layer on at least the upper surface of the contact padregion, depositing a second passivation layer on the first passivationlayer, and depositing a third passivation layer on the secondpassivation layer. In accordance with another embodiment, removing thefirst portion of the passivation layer stack includes removing the thirdand the second passivation layer from above the contact pad region. Inaccordance with another embodiment, removing the third and the secondpassivation layer from above the contact pad region includes an etchprocess. In accordance with another embodiment, the etch processincludes depositing a photoresist layer on the third passivation layer,patterning the photoresist layer such that material of the photoresistlayer is removed from above the contact pad region, etching the thirdand second passivation layer, wherein the first passivation layer isused as an etch stop, and removing the remaining material of thephotoresist layer. In accordance with another embodiment, the remainingmaterial of the photoresist layer is removed using an oxygen plasma or awet chemical etch. In accordance with another embodiment, removing thesecond portion of the passivation layer stack includes removing thefirst passivation layer from the upper surface of the contact padregion. In accordance with another embodiment, removing the firstpassivation layer from the upper surface of the contact pad regionincludes an etch process. In accordance with another embodiment,depositing the third passivation layer includes depositing a layer thathas a greater thickness than the first passivation layer or that isharder to etch than the first passivation layer. In accordance withanother embodiment, depositing the first passivation layer includesdepositing a first nitride layer, depositing the second passivationlayer includes depositing an oxide layer or a carbide layer, anddepositing the third passivation layer includes depositing a secondnitride layer. In accordance with another embodiment, the first nitridelayer has a thickness in the range from about 20 nm to about 200 nm, theoxide layer or the carbide layer has a thickness in the range from about100 nm to about 2 μm, and the second nitride layer has a thickness inthe range from about 100 nm to about 2 μm. In accordance with anotherembodiment, the deposition of at least one of the first, second andthird passivation layer includes a chemical vapor deposition process. Inaccordance with another embodiment, forming the adhesion layer includesdepositing an imide layer. In accordance with another embodiment,patterning the adhesion layer includes removing the adhesion layer fromabove the contact pad region and further from above a third portion ofthe passivation layer stack adjacent to the contact pad region, suchthat a lateral spacing is formed between the adhesion layer and thecontact pad region. In accordance with another embodiment, the lateralspacing has a width in the range from about 1 μm to about 10 μm. Inaccordance with another embodiment, the contact pad region includescopper, aluminum or tungsten. In accordance with another embodiment,forming the reinforcement layer stack includes depositing a firstreinforcement layer on the upper surface of the contact pad region,depositing a second reinforcement layer on the first reinforcementlayer, and depositing a third reinforcement layer on the secondreinforcement layer. In accordance with another embodiment, the firstreinforcement layer includes one or more of the following materials:nickel, a binary material including nickel, a ternarystress-accommodated material. In accordance with another embodiment, thefirst reinforcement layer includes one or more of the followingmaterials: nickel phosphorus (NiP), nickel boron (NiB), NiWP, NiMoP,CoWP. In accordance with another embodiment, the second reinforcementlayer includes one or more of the following materials: palladium (Pd),platinum (Pt), copper (Cu), silver (Ag). In accordance with anotherembodiment, the third reinforcement layer includes one or more of thefollowing materials: gold (Au), platinum (Pt). In accordance withanother embodiment, the deposition of at least one of the first, secondand third reinforcement layer includes an electroless plating process.In accordance with another embodiment, the first reinforcement layer hasa thickness in the range from about 500 nm to about 10 μm, the secondreinforcement layer has a thickness in the range from about 0 to about 1μm, and the third reinforcement layer has a thickness in the range fromabout 0 to about 200 nm.

FIG. 5 shows a diagram 500 that illustrates a method of manufacturing acontact pad of an integrated circuit element in accordance with anembodiment of the invention.

In 502, a passivation layer stack is formed on an upper surface of asurface region of the integrated circuit element, the surface regionincluding a contact pad region, and the passivation layer stackincluding at least one passivation layer. The passivation layer stackmay be formed in accordance with one of the embodiments describedherein.

In 504, a first portion of the passivation layer stack is removed fromabove the contact pad region, wherein a second portion of thepassivation layer stack remains on the contact pad region and covers thecontact pad region. The first portion of the passivation layer stack maybe removed in accordance with one of the embodiments described herein.

In 506, an adhesion layer is formed on the passivation layer stack. Theadhesion layer may be formed in accordance with one of the embodimentsdescribed herein.

In 508, the adhesion layer is patterned, wherein the adhesion layer isremoved from at least above the contact pad region. The patterning ofthe adhesion layer and the removal of the adhesion layer from above thecontact pad region may be achieved in accordance with one of theembodiments described herein.

In 510, the second portion of the passivation layer stack is removedfrom above the contact pad region. The removal of the second portion ofthe passivation layer stack may be achieved in accordance with one ofthe embodiments described herein.

In 512, a reinforcement layer stack is formed on the contact pad regionafter removing the second portion of the passivation layer stack, thereinforcement layer stack including at least one reinforcement layer.

In accordance with one embodiment, forming the passivation layer stackincludes depositing a first nitride layer on the upper surface of thesurface region, depositing an oxide layer on the first nitride layer,and depositing a second nitride layer on the oxide layer. In accordancewith another embodiment, removing the first portion of the passivationlayer stack includes etching the second nitride layer and the oxidelayer from above the contact pad region using the first nitride layer asan etch stop. In accordance with another embodiment, forming thereinforcement layer stack includes depositing a first reinforcementlayer on an upper surface of the contact pad region, depositing a secondreinforcement layer on the first reinforcement layer, and depositing athird reinforcement layer on the second reinforcement layer. Inaccordance with another embodiment, the deposition of at least one ofthe first, second and third reinforcement layer includes an electrolessplating process.

In the following, additional features and effects of exemplaryembodiments of the invention are discussed.

In accordance with an embodiment of the invention, a high-temperatureresistant contact pad or bonding pad is provided on a metallizationregion such as, for example, a copper metallization (alternatively,other metallizations such as, for example, an aluminum or a tungstenmetallization). In one embodiment, the pad surface is coated withpalladium and/or gold. For example, a thin layer of gold is formed on athin layer of palladium.

In another embodiment of the invention, an intermediate layer of, e.g.,nickel is formed on the metallization, for example, on the coppermetallization (alternatively, on the aluminum or tungstenmetallization). This intermediate layer may increase the strength of thepad during a bonding of the pad.

In accordance with another embodiment of the invention, a polyimidelayer is formed on a passivation structure or stack. This polyimidelayer may be used as an adhesion layer for providing adherence to apackage body. In accordance with an embodiment of the invention, thepolyimide layer is formed in such a manner that a mechanical contact ofthe polyimide layer with the copper metallization is avoided. Thus, inaddition to polyimide materials that are compatible with copper, alsopolyimide materials may be used that are not compatible with the coppermaterial of the copper metallization.

In accordance with another embodiment of the invention, a method ofmanufacturing a contact pad of an integrated circuit element isprovided, wherein a planar chip surface or a planar topography isachieved so that improved high voltage characteristics of the pad may beachieved and/or the development of cracks in the pad may be prevented.Thus, high-quality contact pads may be obtained that have favorablehigh-voltage characteristics and are free from cracks.

In accordance with one embodiment of the invention, a passivation layerstack is deposited onto a planar structured copper pad. The copper padmay have been patterned, for example, by a single or dual damascenetechnology. In one embodiment, the passivation layer stack includes afirst silicon nitride (SiN_(x)) layer having a thickness in the rangefrom about 20 nm to about 200 nm, a silicon oxide (SiO₂) layer formed onthe first silicon nitride layer and having a thickness in the range fromabout 100 nm to about 2 μm, and a terminating second silicon nitride(SiN_(x)) layer formed on the silicon oxide layer and having a thicknessin the range from about 100 nm to about 2 μm. The first silicon nitridelayer may serve as a copper diffusion barrier layer, in other words, asa layer that reduces or prevents diffusion of copper material or atoms(from the pad) into the passivation layer stack.

In accordance with an embodiment of the invention, the topmost siliconnitride layer (i.e., the second silicon nitride layer) and the siliconoxide layer of the passivation layer stack are opened above the pad, forexample, using a photoresist mask and an etch process. In oneembodiment, the etching of the passivation layer stack terminates on thelower silicon nitride layer (i.e., the first silicon nitride layer) ofthe passivation layer stack. In other words, the lower silicon nitridelayer of the passivation layer stack may serve as an etch stop layerduring the etching of the passivation layer stack. Thus, the contact pad(e.g., the copper pad) remains fully covered by the first siliconnitride layer so that the contact pad or the contact pad surface (e.g.,the copper surface) is protected against subsequent aggressive processsteps.

In one embodiment, after etching away the second silicon nitride layerand the silicon oxide layer of the passivation layer stack, thephotoresist is removed, for example, by means of an oxygen plasma or awet chemical process. The contact pad surface is protected against theseaggressive process steps by the remaining first silicon nitride layer.

In one embodiment, after removing the photoresist, a photoimide orpolyimide layer is applied to or deposited onto the passivation layerstack (i.e., on the upper surface of the passivation layer stack), andthe photoimide layer is patterned. In one embodiment, the patterning iscarried out in such a way that the polyimide edge (i.e., the edge of thepolyimide layer) is pulled back from the contact pad edge, for example,by several microns (e.g., 5 μm) in one embodiment. Thus, a distance orspacing is formed between the photoimide layer and the contact pad. Thishas, for example, the effect that also photoimide materials may be usedthat are not compatible with copper, in other words, photoimidematerials that react with copper.

In one embodiment, after applying the photoimide layer, a cyclization ofthe photoimide layer is carried out by means of an annealing step, andsubsequently the photoimide layer is post-treated using an oxygenplasma. The contact pad surface is also protected against theseaggressive process steps by means of the remaining first silicon nitridelayer that covers the contact pad.

In accordance with one embodiment, the remaining first silicon nitridelayer is opened or removed by means of a subsequent etch step using theSiO₂/SiN_(x) double layer (that is, the silicon oxide layer and thesecond silicon nitride layer of the passivation layer stack) as a hardmask. In one embodiment, after opening the first silicon nitride layer,subsequent cleaning steps (e.g., removal of polymer material, cleaningof copper surface of the contact pad) are carried out.

In accordance with another embodiment, a pad reinforcement layer stackis then deposited by means of an electrochemical deposition process. Inone embodiment, the pad reinforcement layer stack includes a layersequence including a Ni and/or Ni₃P layer having a thickness in therange from about 500 nm to about 10 μm, a Pd layer formed on the Ni/Ni₃Player and having a thickness in the range from about 0 nm to about 1 μm,and an Au layer formed on the Pd layer and having a thickness in therange from about 0 nm to about 200 nm. In accordance with an embodiment,the total thickness of the reinforcement layer stack may be chosen suchthat the pad surface (that is, the upper surface of the pad having thereinforcement layer stack formed thereon) is flush with the uppersurface of the passivation layer stack.

In accordance with some embodiments of the invention, the formation ofan additional aluminum pad on a copper pad can be saved in areinforcement process of a copper pad.

In accordance with some embodiments of the invention, polyimidematerials that are incompatible with copper may be used in a method ofprocessing and/or reinforcing a copper contact pad.

In accordance with some embodiments of the invention, a planartopography or a planar chip surface may be achieved in a method ofmanufacturing a contact pad of an integrated circuit element.

In accordance with some embodiments of the invention, a two-stageetching process is applied to etch a three-layer passivation layerstack, and a copper pad formed below the passivation layer stack isreinforced directly. In accordance with some embodiments, the coppersurface of the pad may be protected against aggressive process steps(such as, for example, aggressive etching steps) and the padreinforcement layers may be sunk in the passivation.

In accordance with some embodiments of the invention, methods ofprocessing or manufacturing a contact pad (or a plurality of contactpads) of an integrated circuit element are provided. In accordance withone embodiment, the contact pad(s) or the integrated circuit element maybe part of an integrated electronic device, such as, for example, anintegrated memory device or an integrated logic device.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

1. A method of processing a contact pad, the method comprising: forminga passivation layer stack over at least an upper surface of a contactpad region, the passivation layer stack comprising at least onepassivation layer; removing a first portion of the passivation layerstack from above the contact pad region, wherein a second portion of thepassivation layer stack remains on the contact pad region and covers thecontact pad region; forming an adhesion layer on the passivation layerstack; patterning the adhesion layer, wherein the adhesion layer isremoved from above the contact pad region; and removing the secondportion of the passivation layer stack.
 2. The method of claim 1,further comprising: forming a reinforcement layer stack over the contactpad region after removing the second portion of the passivation layerstack, the reinforcement layer stack comprising at least onereinforcement layer.
 3. The method of claim 2, wherein forming thereinforcement layer stack comprises: depositing a first reinforcementlayer on the upper surface of the contact pad region; depositing asecond reinforcement layer on the first reinforcement layer; anddepositing a third reinforcement layer on the second reinforcementlayer.
 4. The method of claim 3, wherein depositing of at least one ofthe first, second and/or third reinforcement layers comprises anelectroless plating process.
 5. The method of claim 1, wherein formingthe passivation layer stack comprises: depositing a first passivationlayer on at least the upper surface of the contact pad region;depositing a second passivation layer on the first passivation layer;and depositing a third passivation layer on the second passivationlayer.
 6. The method of claim 5, wherein removing the first portion ofthe passivation layer stack comprises removing the third and the secondpassivation layer from above the contact pad region.
 7. The method ofclaim 6, wherein removing the third and the second passivation layerfrom above the contact pad region comprises an etch process.
 8. Themethod of claim 7, wherein the etch process comprises: depositing aphotoresist layer over the third passivation layer; patterning thephotoresist layer such that material of the photoresist layer is removedfrom above the contact pad region; etching the third and secondpassivation layer, wherein the first passivation layer is used as anetch stop; and removing remaining material of the photoresist layer. 9.The method of claim 6, wherein removing the second portion of thepassivation layer stack comprises removing the first passivation layerfrom the upper surface of the contact pad region.
 10. The method ofclaim 5, wherein depositing the third passivation layer comprisesdepositing a layer that has a greater thickness than the firstpassivation layer or that is harder to etch than the first passivationlayer.
 11. The method of claim 5, wherein depositing the firstpassivation layer comprises depositing a first nitride layer, whereindepositing the second passivation layer comprises depositing an oxidelayer or a carbide layer, and wherein depositing the third passivationlayer comprises depositing a second nitride layer.
 12. The method ofclaim 1, wherein patterning the adhesion layer comprises removing theadhesion layer from above the contact pad region and further from abovea third portion of the passivation layer stack adjacent to the contactpad region, such that a lateral spacing is formed between the adhesionlayer and the contact pad region.
 13. The method of claim 1, wherein thecontact pad region comprises copper, aluminum or tungsten.
 14. A methodof manufacturing an integrated circuit, the method comprising: forming apassivation layer stack comprising at least one passivation layer, overan upper surface of a surface region of the integrated circuit element,the surface region comprising a contact pad region; removing a firstportion of the passivation layer stack from above the contact padregion, wherein a second portion of the passivation layer stack remainson the contact pad region and covers the contact pad region; forming anadhesion layer on the passivation layer stack; patterning the adhesionlayer, wherein the adhesion layer is removed from at least above thecontact pad region; removing the second portion of the passivation layerstack from above the contact pad region; and forming a reinforcementlayer stack on the contact pad region after removing the second portionof the passivation layer stack, the reinforcement layer stack comprisingat least one reinforcement layer.
 15. The method of claim 14, whereinforming the passivation layer stack comprises: depositing a firstnitride layer on the upper surface of the surface region; depositing anoxide layer on the first nitride layer; and depositing a second nitridelayer on the oxide layer.
 16. The method of claim 15, wherein removingthe first portion of the passivation layer stack comprises etching thesecond nitride layer and the oxide layer from above the contact padregion using the first nitride layer as an etch stop.